KR101961944B1 - Transparent ceramic, method for manufacturing same, and magneto-optical device - Google Patents

Abstract

A ceramics comprising, as a main component, at least one oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxide, terbium oxide (Tb ₂ O ₃ ) in a molar ratio of at least 40% (2) the average crystal grain diameter is in the range of 0.5 to 100 占 퐉; (3) the crystal structure of the above-mentioned ceramics of the terephthalate type has an abnormality other than the cubic crystal Wherein the sintering aid does not precipitate. The transparent ceramics according to the present invention can provide a magneto-optical device having a performance equal to or higher than that of a single crystal material such as a conventional terbium gallium garnet. It is possible to provide a functional device in an optical isolator in an infrared region in which the birefringence component is extremely small and scattering is extremely small and the wavelength is 500 nm or more and 1.5 占 퐉 or less even in optical loss and optical uniformity.

Description

TRANSPARENT CERAMIC, METHOD FOR MANUFACTURING SAME, AND MAGNETO-OPTICAL DEVICE,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent ceramics which is effective for a magneto-optical device, which is used for constructing a magneto-optical device such as an optical isolator, and a method of manufacturing the same.

The present invention also relates to a magneto-optical device such as a Faraday rotator and an optical isolator.

2. Description of the Related Art In recent years, a magneto-optical device using the interaction between light and magnet has been attracting attention as the laser processing machine progresses. One of them is an isolator, which suppresses the phenomenon that the light emitted from the laser light source is reflected by the optical system in the middle and returns to the light source, causing the light emitted from the laser light source to propagate and becoming an unstable oscillation state. Therefore, by using this action, the optical isolator is disposed between the laser light source and the optical component.

The optical isolator has three components: a Faraday rotator, a polarizer disposed on the light incident side of the Faraday rotator, and an analyzer disposed on the light exit side of the Faraday rotator. The optical isolator utilizes the so-called Faraday effect that the polarization plane rotates in the Faraday rotator when the light is incident on the Faraday rotator in a state where a magnetic field is applied parallel to the traveling direction of the light to the Faraday rotator. That is, in the incident light, light having the same polarization plane as that of the polarizer passes through the polarizer and is incident on the Faraday rotator. This light is rotated by plus 45 degrees with respect to the traveling direction of the light in the Faraday rotator, and is emitted.

On the other hand, the return light incident on the Faraday rotator from the direction of incidence passes through the analyzer only when the light having the same polarization plane as that of the analyzer passes through the analyzer for the first time, . Next, in the Faraday rotator, since the polarization plane of the return light is further rotated by plus 45 degrees from the first plus 45 degrees, it becomes a polarization plane perpendicular to the polarizer and plus 90 degrees, and the return light can not transmit the polarizer.

The Faraday rotation angle? Is expressed by the following equation (A).

? = V 占 H 占 L (A)

In the equation (A), V is a Verdet constant and a constant determined by the material of the Faraday rotator, H is the magnetic flux density, and L is the length of the Faraday rotator. When used as an optical isolator, L is determined so that? = 45 degrees.

In the material used as the Faraday rotator of the optical isolator as described above, it is important that the Faraday effect is large and the transmittance is high at the wavelength used.

Further, when a polarized light component different from the incident light is generated in the emitted light, the different polarized light components pass through the polarizer, so that the blocking of the returned light becomes insufficient.

As the evaluation of the state of occurrence of these different polarized components, polarized light of 0 degree to 90 degrees is applied to a material usable as a Faraday rotator, the emitted light is incident on a light receiver through a polarizer, And the extinction ratio S is calculated from the maximum value Imax and the minimum value Imin by the following equation and evaluated.

S = -10 log (Imin / Imax) [unit dB]

It is important that the extinction ratio is large, and generally, 30 dB or more is required.

Recently, as a material thereof, Japanese Patent Application Laid-Open No. 2010-285299 (Patent Document 1) discloses an oxide single crystal and transparent oxide ceramics of (Tb _x Re _{1 -x} ) ₂ O ₃ : Lt; / RTI >

Further, in Japanese Patent No. 4033451 (Patent Document 2), the rare-earth oxide represented by the general formula R ₂ O ₃ (R: rare-earth element) has a cubic crystal structure and no birefringence. Therefore, it is described that it is possible to obtain a sintered body having excellent transparency by completely removing segregation of pores and impurities.

Further, as disclosed in Japanese Unexamined Patent Application Publication No. 5-330913 (Patent Document 3), addition of a sintering auxiliary agent is effective for removing pores. As disclosed in Japanese Patent No. 2638669 (Patent Document 4), a method of re-sintering after the hot isostatic pressing step and removing pores is also disclosed. As a sintering aid, one or a plurality of sintering aids as disclosed in Japanese Unexamined Patent Application Publication No. 5-330913 (Patent Document 5) are added, mixed, molded, sintered under vacuum, and subjected to HIP treatment.

However, in Japanese Unexamined Patent Application Publication No. 2010-285299 (Patent Document 6), transparent oxide ceramics of (Tb _x Re _{1 -x} ) ₂ O ₃ : 0.4? X? 1.0 basically have a cubic crystal structure, The sintering assistant reacts with the main component, and a phase different from the cubic phase precipitates in the grain boundaries or in the grain boundaries, resulting in some cases of birefringence. Therefore, the extinction ratio may be lowered.

Further, since the precipitate has a minute size of 1 μm or less, when the laser beam is irradiated, the laser beam is scattered there, and the insertion loss is sometimes lowered by scattering.

When the ceramics are sintered, the composition of the main component (Tb _x Re _{1 -x} ) ₂ O ₃ and the concentration of the sintering auxiliary agent are segregated in the inside and the outside of the ceramics, and the deviation of the extinction ratio and the insertion loss .

Japanese Patent Application Laid-Open No. 2010-285299 Japanese Patent No. 4033451 Japanese Patent Laid-Open Publication No. 5-330913 Japanese Patent No. 2638669 Japanese Patent Laid-Open Publication No. 5-330913 Japanese Patent Application Laid-Open No. 2010-285299

It is an object of the present invention to provide a transparent ceramics which is effective for a magneto-optical material of a rare-earth oxide containing terbium oxide having a large Verde constant at a wavelength of 1.06 mu m (0.9-1.1 mu m), has high uniformity and transparency in a plane, Optical ceramics and a method for producing the transparent ceramics, which can reduce the insertion loss and increase the extinction ratio, thereby making it possible to improve the properties of the magneto-optical material. It is still another object of the present invention to provide a high-quality magneto-optical device suitably used for a fiber laser for a processing machine.

Ceramics containing terbium oxide and rare earths (scandium, yttrium, lanthanum, europium, gadolinium, ytterbium, holmium and lutetium) oxides as main components are easily scattered and have a large insertion loss and conversely have a small extinction ratio. It is extremely difficult to apply it to an optical material such as an optical isolator.

On the other hand, in the present invention, it is preferable to use a starting material having a specific particle size distribution which is excellent in sintering property, (2) a sintering aid which has good sinterability and can maintain the crystal structure of the ceramics at cubic, (4) sintering the sintered body obtained in the above (3) by pressurizing and sintering so as to obtain scattering It is possible to provide an optically uniform optical rare-earth oxide-based optical ceramics having less fluctuation of the composition by reducing precipitates or pores which cause a large amount of crystal grains.

That is, the present invention provides the following transparent ceramics, a process for producing the same, and a magneto-optical device using the transparent ceramics.

[One]

A ceramics mainly composed of at least one oxide selected from ytterbium oxide, scandium oxide and lanthanide rare-earth oxide, terbium oxide (Tb ₂ O ₃ ) in a molar ratio of 40% or more,

(1) the crystal structure of the terephthalate-based ceramics does not contain any abnormality other than cubic crystal,

(2) the average crystal grain diameter is in the range of 0.5 to 100 mu m,

(3) A transparent ceramics characterized by containing a sintering aid which does not precipitate a crystal other than cubic crystal in the crystal structure of the above-mentioned terephthalate-based ceramics.

[2]

The transparent ceramics according to [1], wherein the sintering aid is an oxide, fluoride or nitride of an element selected from titanium, zirconium, hafnium and calcium.

[3]

In the thickness direction of the sample having a thickness of 10 mm,

(1) a linear transmittance at a wavelength of 1,000 nm is 70% or more,

(2) a linear transmittance of at least 55% at a wavelength of 600 nm

The transparent ceramics described in [1] or [2].

[4]

The transparent ceramics described in any one of [1] to [3], wherein an insertion loss including a reflection loss at a cross section in a plane of 90% or more of a measurement plane at a wavelength of 1,065 nm is 1.2 dB or less.

[5]

The transparent ceramics described in any one of [1] to [4], wherein the extinction ratio in the plane of not less than 90% of the measurement surface is not less than 30 dB at a wavelength of 1,065 nm.

[6]

The transparent ceramics described in any one of [1] to [5], wherein the refractive index distribution at the time of measurement of the transmission wave front in the region of 90% or more of the measurement surface at a thickness of 10 mm is within 5 × 10 ^-5 at a wavelength of 633 nm.

[7]

A method for producing a transparent ceramics,

(1) (a) terbium oxide,

(b) at least one oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides,

(c) a sintering aid which does not precipitate the crystal other than the cubic crystal in the crystal structure of the terephthalate-based ceramics

A first step of pulverizing and mixing each raw material powder having an average primary particle diameter of 30 to 2,000 nm and then molding to obtain a molded article,

(2) a second step of calcining the shaped body at 200 to 1,000 DEG C in a non-oxidative or oxidative atmosphere to obtain a calcined body,

(3) a third step of obtaining a sintered body by firing the calcined body at 1,400 to 1,700 DEG C in a non-

(4) The fourth step of obtaining the pressure-fired body by pressure-firing the sintered body at a pressure of 19 to 196 MPa at 1,400 to 1,800 占 폚

Wherein the transparent ceramics has a thickness of from about 1 to about 10 nm.

[8]

A method for producing a transparent ceramics,

(1) (a) terbium oxide,

(b) at least one oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides,

(c) a sintering aid which does not precipitate the crystal other than the cubic crystal in the crystal structure of the terephthalate-based ceramics

And a powder having a mean primary particle diameter of 30 to 2,000 nm is pulverized and mixed, and then calcined at 200 to 1,000 占 폚 in a non-oxidizing or oxidizing atmosphere to obtain a compact ,

(2) a second step of obtaining a sintered body by firing the molded body at 1,400 to 1,700 DEG C in a non-

(3) a third step of pressurizing and firing the sintered body at a pressure of 19 to 196 MPa at 1,400 to 1,800 ° C to obtain a pressure-

Wherein the transparent ceramics has a thickness of from about 1 to about 10 nm.

[9]

A method for producing a transparent ceramics,

(1) (d) terbium ions,

(e) at least one rare earth ion selected from yttrium ions, scandium ions and lanthanide rare earth ions

Wherein the mixed powder contains terbium oxide in a molar ratio of 40% or more, and the mixed powder has an average primary particle diameter of 30 to 2,000 nm by coprecipitation, filtration and calcination, A first process comprising an oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides,

(2) a second step of grinding and mixing the mixed powder and an oxide, fluoride or nitride of an element selected from titanium, zirconium, hafnium and calcium as a sintering aid,

(3) a third step of obtaining a sintered body by firing the molded body at 1,400 to 1,700 DEG C in a non-

(4) Fourth step of obtaining the pressure-sintered body by pressure-baking the sintered body at a pressure of 19 to 196 MPa at 1,400 to 1,800 占 폚

Wherein the transparent ceramics has a thickness of from about 1 to about 10 nm.

[10]

A production method according to claim 7, 8 or 9, wherein the pressure-fired sintered body is obtained and then annealed at 1,500 to 2,000 ° C in an atmosphere containing no oxygen.

[11]

A magneto-optical device comprising the transparent ceramics described in any one of [1] to [6].

[12]

A magneto-optical device in which the transparent ceramics described in any one of [1] to [6] is used as a Faraday rotation element.

[13]

The magneto-optical device according to [12], wherein the magneto-optical device is used in a wavelength region of 1,065 nm with a polarizing material before and after the Faraday rotator.

The transparent ceramics according to the present invention can obtain excellent optical characteristics in the visible to infrared region, which is not obtained in the tunable ceramics reported in Japanese Patent Laid-Open Publication No. 2010-285299, and is superior to the conventional single crystal materials such as terbium gallium garnet It is possible to provide a magneto-optical device having a higher performance.

Further, optical loss and optical uniformity are superior to those of conventional ceramics materials, so that a birefringent component is extremely small and scattering is extremely small, and a functional device in an optical isolator in an infrared region of about 500 nm or more and 1.5 μm or less can be provided .

1 is a flow sheet showing an example of a method for producing polycrystalline transparent rare earth oxide ceramics.
2 is a transmittance measurement profile of transparent ceramics.
3 is a conceptual diagram of an isolator.

Transparent ceramics

The transparent ceramics of the present invention comprises at least one selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides having a molar ratio of terbium oxide (Tb ₂ O ₃ ) of 40% or more and an absorption of 1% or less at a wavelength of 1.065 μm As ceramics containing oxides as a main component,

(1) the crystal structure of the terephthalate-based ceramics does not contain any abnormality other than cubic crystal,

(2) the average crystal grain diameter is in the range of 0.5 to 100 mu m,

(3) A sintering aid composition containing a sintering auxiliary agent which does not precipitate a crystal other than the cubic phase in the crystal structure of the above-mentioned terephthalate-based ceramics

.

In this case, when (a) terbium oxide and (b) oxide have a total content of 1 (100 mol%) as a molar ratio, (a) terbium oxide is 40 mol% or more, preferably 40 to 60 mol% And the remainder is the oxide (b). Practically, the ceramics of the present invention are composed of the components (a) and (b) and the sintering auxiliary agent.

It is known that the terbium oxide phase undergoes phase transition from cubic to monoclinic at around 1,400 to 1,600 ° C. Therefore, when ceramics of rare earth oxides containing terbium oxide are sintered at 1,400 to 1,600 DEG C, the phase transition is necessarily caused in the cubic phase from sintering or cooling. Therefore, if the phase transition does not occur and a part of the monoclinic crystal remains, the portion becomes an ideal precipitate, which causes scattering. Further, since the uniaxiality is anisotropic, birefringence is exhibited. Therefore, it is preferable to add a sintering auxiliary agent capable of smooth phase transition from cubic to cubic. As the sintering aid, a 4A group element such as titanium, zirconium, or hafnium, calcium, scandium, or yttrium, or a lanthanide element in which absorption is absent near a wavelength of 1.06 mu m may be used.

First, they do not absorb near a wavelength of 1.06 mu m. Further, since the element 4A is used as a stabilizing fire when sintering yttrium oxide, it is also effective as a stable fire in a rare earth oxide containing terbium oxide of the present invention. Since calcium has strong ionicity, it has high reactivity and is liable to be dissolved in rare earth oxides. Elements other than these can not be reacted as sintering aids because they are absorbed in the vicinity of a wavelength of 1.06 mu m or are difficult to be solidified with rare earth oxides. Therefore, they are not precipitated singly or have an excessively high activity, There is a problem that it can not be made into an optimum range or that the ceramic reacts slowly with moisture in a long period of time to exhibit hygroscopicity and to be disappeared.

As the sintering aid, an element selected from titanium, zirconium, hafnium and calcium is preferable. When these elements are incorporated as sintering aids, oxides are most preferable, but fluorides, nitrides and carbides may be used.

The content of these elements as a sintering auxiliary agent is preferably 0.001 to 1% by mass, and more preferably 0.01 to 1% by mass, based on the total amount of the transparent ceramics. If it is less than this range, a stable effect as a sintering aid can not be obtained. On the other hand, if it is larger than the above range, it can not be solidified and precipitates singly and causes scattering.

The ceramics of the present invention are polycrystals. The average crystal grain diameter is usually in the range of 0.5 to 100 mu m, preferably in the range of 1 to 50 mu m. If the average crystal grain diameter exceeds 100 탆, impurities are likely to precipitate in the grain boundary portion, bubbles tend to remain in the grain or the grain boundary portion, causing not only light scattering but also insufficient thermal mechanical properties have. In the present invention, the average crystal grain diameter is an average value of the long diameter of 100 crystal grains in an arbitrary field of view by observation with a scanning electron microscope or an optical microscope.

(1) the linear transmittance in the baseline of light transmission at a wavelength of 1,000 nm is 70% or more (preferably 72% or more), (2) It is preferable that the linear transmittance in the baseline of light transmission at a wavelength of 600 nm is 55% or more, preferably 60% or more (more preferably 65% or more).

When the linear transmittance of (1) is less than 70%, or when the linear transmittance of (2) is less than 55%, light scattering at crystal grains or grain boundaries is extremely large, or light absorption at crystal grains is very large, It is difficult to use for the purpose of the present invention. In the present invention, the term " baseline " means the absorption spectrum of the sintering aid or the rare-earth oxide such as terbium oxide when the absorption is expressed in the transmission spectrum of the wavelength-transmittance. In the present invention, a sample having a diameter of 6 mmφ and a thickness of 10 mm obtained by polishing a surface roughness Rms of 1 nm or less is used as the linear transmittance by using a spectrometer "Spectrometer, trade name U3500" (trade name, manufactured by Hitachi, , The beam diameter is measured in the size of 1 to 3 mm ?.

(1) the insertion loss is 1.2 dB or less, particularly 1 dB or less, in a plane of 90% or more of the measurement plane at a wavelength of 1,065 nm, (2) the wavelength At 1,065 nm, the extinction ratio is preferably 30 dB or more within a plane of 90% or more of the measurement surface.

When the insertion loss of the above (1) exceeds 1.2 dB, the light scattering at the crystal grains or grain boundaries is very large, or the light absorption at the crystal grains is very large, so that it may be difficult to use for the purposes of the present invention. When the extinction ratio of (2) is less than 30 dB, the crystal grain or the birefringence at the grain boundaries is very large, so that it may be difficult to use it for the purposes of the present invention.

In the present invention, the insertion loss is determined by placing the ceramics on a V block, coherent light of several mW at a wavelength of 1.065 mu m is incident perpendicularly to the ceramics, and light intensity is measured by a semiconductor light receiver. At this time, the light intensity when the ceramics are not inserted is used as a base, and the decrease in light intensity with respect to the light intensity is expressed in dB. A sample having a diameter of 6 mm and a thickness of 10 mm is used which has a surface roughness Rms of not more than 1 nm, a surface flatness of not more than? / 4, and a parallelism of both end faces of not more than 0.5 degrees. The measurement also includes surface reflections on both sides.

Further, the V block on which the ceramics are mounted can move in the direction perpendicular to the incident light, and thereby the in-plane distribution of the ceramics can be measured. Therefore, the in-plane distribution of 90% or more of the measurement surface is the result of measurement at each measurement point while moving the V-shaped block to 95% of the diameter.

In the present invention, the above-mentioned extinction ratio is obtained by placing the ceramics on a V-block, applying 0-degree and 90-degree polarized coherent light of several mW with respect to the material to a wavelength of 1.065 탆, The intensity of the light is measured in the light receiver and expressed in units of dB from the maximum value (Imax) and the minimum value (Imin). A sample having a diameter of 6 mm and a thickness of 10 mm is used which has a surface roughness Rms of not more than 1 nm, a surface flatness of not more than? / 4, and a parallelism of both end faces of not more than 0.5 degrees. Further, the V block on which the ceramics are mounted can move in the vertical direction with respect to the incident light, whereby the in-plane distribution of the ceramics can be measured. Therefore, the in-plane distribution of 90% or more of the measurement surface is the result of measurement at each measurement point while moving the V-shaped block to 95% of the diameter.

In addition, the refractive index distribution at the time of transmitting the wave front measurement at least 90% of the measured surface area at a thickness of 10mm at a wavelength of 633nm 5 × 10 ^-5 or less, and more preferably from ^{1 × 10 -6 ~2 × 10 -5} . The refractive index distribution can be obtained by measuring the sample transmission wavefront at a wavelength of 633 nm using a optical interferometer G102 manufactured by Fuji Photo Film.

Manufacturing method of transparent ceramics

The transparent ceramics of the present invention is preferably formed by any one of the following first to third methods.

≪ First method > Solid phase reaction

A method for producing a transparent ceramics,

(1) (a) terbium oxide,

(b) at least one oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides,

(c) a sintering aid which does not precipitate the crystal other than the cubic crystal in the crystal structure of the terephthalate-based ceramics

A first step of pulverizing and mixing each raw material powder having an average primary particle diameter of 30 to 2,000 nm and then molding to obtain a molded article,

(2) a second step of calcining the shaped body at 200 to 1,000 DEG C in a non-oxidative or oxidative atmosphere to obtain a calcined body,

(3) a third step of obtaining a sintered body by firing the calcined body at 1,400 to 1,700 DEG C in a non-

(4) Fourth step of obtaining the pressure-sintered body by pressure-baking the sintered body at a pressure of 19 to 196 MPa at 1,400 to 1,800 占 폚

≪ / RTI >

≪ Second method > Solid phase reaction

A method for producing a transparent ceramics,

(1) (a) terbium oxide,

(b) at least one oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides,

(c) a sintering aid which does not precipitate the crystal other than the cubic crystal in the crystal structure of the terephthalate-based ceramics

And a powder having a mean primary particle diameter of 30 to 2,000 nm is pulverized and mixed, and then calcined at 200 to 1,000 占 폚 in a non-oxidizing or oxidizing atmosphere to obtain a compact ,

(2) a second step of obtaining a sintered body by firing the molded body at 1,400 to 1,700 DEG C in a non-

(3) a third step of pressurizing and firing the sintered body at a pressure of 19 to 196 MPa at 1,400 to 1,800 ° C to obtain a pressure-

≪ / RTI >

<Third Method>

A method for producing a transparent ceramics,

(1) (d) terbium ions,

(e) at least one rare earth ion selected from yttrium ions, scandium ions and lanthanide rare earth ions

And a calcining step of subjecting an aqueous solution containing the cerium oxide powder to coprecipitation, filtration and calcination to prepare a mixed powder having an average primary particle diameter of 30 to 2,000 nm in advance, wherein the mixed powder contains terbium oxide in a molar ratio of 40% , A yttrium oxide, a scandium oxide and a lanthanide rare earth oxide,

(2) a second step of grinding and mixing the mixed powder and an oxide, fluoride or nitride of an element selected from titanium, zirconium, hafnium and calcium as a sintering aid,

(3) a third step of obtaining a sintered body by firing the molded body at 1,400 to 1,700 DEG C in a non-

(4) Fourth step of obtaining the pressure-sintered body by pressure-baking the sintered body at a pressure of 19 to 196 MPa at 1,400 to 1,800 占 폚

&Lt; / RTI &gt;

(B) at least one selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides having little absorption (less than 1%) at a wavelength of 1.065 占 퐉 in the first step of the first and second methods; (C) a sintering aid which does not precipitate a crystal other than the cubic crystal in the crystal structure of the above-mentioned terebium oxide-based ceramics, and in this case also has an average primary particle diameter of 30 to 2,000 nm, 2,000 nm are used, and these are pulverized and mixed. The molar ratio of terbium oxide to the oxide of (b) is 40 mol% or more, preferably 40 to 60 mol%, and the oxide of (b) is the remainder.

Terbium oxide can be prepared by a known production method or a commercially available product, but in general, Tb ₄ O ₇ is used instead of Tb ₂ O ₃ . Therefore, the raw material is used as Tb ₄ O _{7. It} is reduced in a high-temperature gas atmosphere containing hydrogen at 1,000 ° C. or higher, stored in a high-temperature atmosphere of 1,000 ° C. or higher, and then quenched to Tb ₂ O ₃ , May be used. The purity of terbium oxide is preferably 99% by mass or more, but is preferably 99.9% by mass or more for use in optical applications.

The purity of yttrium oxide, scandium oxide or lanthanide rare earth oxide which has little absorption at a wavelength of 1.065 μm used as a raw material is preferably 99% by mass or more, but 99.9% by mass or more is preferable for use in optical use.

As a sintering aid which does not precipitate the crystal other than the cubic crystal structure of the above-mentioned crystal structure of the above-mentioned terephthalic ceramics, absorption is not observed in the 4A group element such as titanium, zirconium or hafnium, calcium, scandium or yttrium, Lanthanide element, and titanium, zirconium, hafnium and calcium are particularly preferable. In order to use these high purity ones, an oxide form is preferable, and a purity of 99% by mass or more is preferable, but 99.9% by mass or more is preferable for use in optical use. The content of these elements as a sintering auxiliary agent is preferably 0.001 to 1% by mass, and more preferably 0.01 to 1% by mass.

The primary particle diameter of the raw material powder used in the first step is preferably 30 to 2,000 nm, more preferably 100 to 2,000 nm, and particularly preferably 200 to 1,000 nm. When the primary particle diameter is less than 30 nm, there is a problem that handling is difficult, for example, it is difficult to form, the density of the green compact is low, the shrinkage rate during sintering is large, and cracks tend to occur. When the primary particle diameter exceeds 2,000 nm, the sintering property of the raw material is insufficient, and it is difficult to obtain a high-density and transparent sintered body. The measurement of the primary particle diameter can be performed by the same method as the measurement of the average crystal grain diameter.

When these components are mixed, they can be carried out by using a common mixing and grinding medium such as pot mill. The milling medium is preferably a partially stabilized zirconium oxide ball. This is because zirconia can also be used as a sintering aid and there is no need to worry about the incorporation of zirconia from the zirconia balls.

When at least one of a dispersing agent and a binder is added to the pot mill in addition to the raw material powder and sintering auxiliary agent as required and the organic solvent such as pure water or ethanol is used as the solvent for mixing for several hours to a dozen hours do. As the dispersant and the binder, any of those which can be used for the production of this kind of ceramics can be used. Examples thereof include dispersants such as ammonium polyacrylate and ammonium polycarboxylate, and dispersants such as methylcellulose, ethylcellulose and polyvinyl alcohol Binders can be used in commercial quantities.

The obtained slurry was granulated to a size of several tens of micrometers by solvent removal and granulation by a spray drier, and then the granules were subjected to primary molding in a predetermined mold, CIP (Cold Isostatic Press) method The molded body can be suitably manufactured.

In the first method, in the first method, the compact is subjected to the pulverization / mixing treatment and then molded to obtain a compact. The compact is calcined in a non-oxidizing or oxidizing atmosphere at 200 to 1,000 占 폚 and calcined at 1,400 to 1,700 占 폚 in a non- To obtain a sintered body. On the other hand, in the second method, after the pulverizing and mixing treatment, the calcined powder is calcined at 200 to 1,000 at a non-oxidizing or oxidizing atmosphere to obtain a compact, and the compact is calcined at 1,400 to 1,700 DEG C in a non- And fired to obtain a sintered body. In this case, according to the first method, there is an advantage that the binder used in the molding can be oxidized and removed by calcination. According to the second method, it is possible to suppress the change in atomic number of terbium oxide by firing in a non-oxidizing atmosphere There is an advantage.

In the first method, as a method of obtaining a molded body, a method of molding by press molding using a metal mold and then CIP (cold isostatic pressing) method may be employed.

In the first and second methods, the calcination is performed at 200 to 1,000 DEG C, more preferably 400 to 1,000 DEG C, and still more preferably 600 to 1,000 DEG C. The calcining atmosphere may be an oxidizing atmosphere or a non-oxidizing atmosphere, and the oxidizing atmosphere may be in the atmosphere. The non-oxidizing atmosphere may be a vacuum (for example, 10 ² Pa to 10 ^-5 Pa), a reducing atmosphere, or an inert gas atmosphere . The calcination time varies depending on the calcination temperature, but it is generally about 60 to 180 minutes.

The obtained calcination powder can be molded in the same manner as described in the first method. When the molded body is to be sintered, the sintered body is obtained by firing the molded body at 1,400 to 1,800 ° C, preferably 1,400 to 1,600 ° C. The firing atmosphere is not particularly limited as long as it is an atmosphere in which the terbium oxide Tb ₄ O ₇ is changed to Tb ₂ O _3. For example, it may be in a vacuum, in a reducing atmosphere, or in an inert gas atmosphere. And in the case of carrying out in vacuum, it can be performed under the condition of 10 ² Pa to 10 ^-5 Pa. The firing time varies depending on the firing temperature, but generally it is about 30 to 480 minutes. In this step, the relative density of the sintered body is preferably 90% or more, more preferably 95% or more.

Next, in the first and second methods, the obtained fired body is pressure fired at 1,400 to 1,800 占 폚 in a non-oxidizing atmosphere to obtain a pressure fired body. The method of pressurizing and firing is not particularly limited and may be any of HP (Hot Press) method, HIP (Hot Isostatic Press) method, and the like. Particularly, in the present invention, the HIP method, which is less prone to deformation due to uniform pressure, can be suitably used. For example, transparent ceramics can be obtained by press-baking argon gas as a pressure medium at a pressure in the range of 19 to 196 MPa for 1 to 10 hours, particularly 1 to 5 hours, and 1,400 to 1,800 占 폚.

The third method is a method in which terbium ions and rare earth ions selected from yttrium ions, scandium ions, and lanthanide rare earth ions are allowed to coexist by a method of precipitating an aqueous solution of hydrogencarbonate by ammonia, filtering the resultant, 2 method, calcined mixed powder comprising terbium oxide and an oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides is obtained. In this case, since the mixed powder needs to contain at least 40% of terbium oxide in a molar ratio, the terbium ion in the aqueous solution is adjusted and contained to obtain such a molar ratio. The average primary particle diameter of the mixed powder is preferably 30 to 2,000 nm, more preferably 30 to 1,000 nm, particularly preferably 30 to 800 nm.

Next, the obtained mixed powder is pulverized and mixed with oxides, fluorides or nitrides of elements selected from titanium, zirconium, hafnium and calcium as a sintering aid, and is then fired at 1,400 to 1,700 ° C, more preferably at 1,400 to 1,600 ° C Firing is carried out in the same manner as in the first and second methods under a mild atmosphere to obtain a sintered body and a press sintered body is obtained in the same manner as in the first and second methods.

In the present invention, it is preferable to further carry out the following steps, if necessary. That is, the press fired body obtained above is annealed at 1,500 to 2,000 DEG C in an atmosphere containing no oxygen. Hereinafter, it is referred to as an annealing process.

In the step of obtaining the pressure-fired sintered body, in the ceramics containing terbium oxide, there is a possibility that the number of valences of terbium is not all three and crystal defects accompanied therewith are generated, It is possible to consider absorption. The other is known that phase transition occurs from cubic to monoclinic at around 1,400 to 1,600 DEG C in the terbium oxide single crystal. Therefore, during sintering or cooling, a phase transition occurs from the monoclinic phase to the cubic phase. However, if the phase transition does not occur and a part of the monoclinic phase remains, the portion becomes an abnormal precipitate and causes scattering.

Therefore, in order to solve these problems, the pressurized and sintered body is annealed at 1,500 to 2,000 DEG C in an atmosphere containing no oxygen so that all of the terbium atoms are transposed in the annealing step, All phases are transformed. As a condition of the annealing process, the annealing atmosphere may be any atmosphere as long as it does not contain oxygen, for example, in vacuum, in a reducing atmosphere, or in an inert gas atmosphere. Further, in the case of carrying out in vacuum, it can be performed under the condition of 10 ² Pa to 10 ^-5 Pa. The annealing temperature is 1,500 to 2,000 deg. C, preferably 1,500 to 1,800 deg. The annealing time varies depending on the annealing temperature, but is generally 2 to 100 hours, preferably 10 to 80 hours. The cooling time after annealing may be any time during which cracks do not occur, and is generally 2 to 100 hours, preferably 2 to 50 hours.

In the transparent ceramics thus obtained, carbon, tungsten as a heater material, aluminum, silicon, calcium or the like as a heat insulating material are adhered from a heated heater to the outer peripheral portion of the ceramics in the calcining step, the sintering step, the pressure sintering step and the annealing step, It is necessary to remove both sides in the thickness direction by chemical etching, mechanical grinding or polishing since they act as impurities and allow the transparent ceramics to be devitrified.

The chemical etching may be an inorganic acid such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid or the like or an organic acid such as malic acid or citric acid as long as it is an acidic aqueous solution. For example, in the case of hydrochloric acid, the outer circumferential surface can be etched away by several hundreds of 탆 by heating at 60 캜 or more.

In the case of mechanical grinding, it may be a centerless grinding apparatus or a cylindrical grinding apparatus as long as it is an outer circumferential surface. If both end faces are used, a plane grinding apparatus may be used to reduce several hundreds of 탆 to several millimeters.

If polishing, diamond polishing may be carried out using diamond slurry, SiC slurry or the like, followed by precision polishing of colloidal silica or the like to polish several hundreds of micrometers to several millimeters.

By performing these chemical etching, mechanical grinding or polishing, an optical element having excellent optical characteristics can be formed.

Magneto-optic material

The oxide, oxide single crystal and ceramics of the present invention are suitable for use in magneto-optical materials. Particularly, the oxide, oxide single crystal and ceramics of the present invention are suitably used as a Faraday rotator of an optical isolator having a wavelength of 0.9 to 1.1 탆, particularly a wavelength of 1,065 nm.

3 is a schematic cross-sectional view showing an example of an optical isolator, which is an optical device having a Faraday rotator as an optical element.

3, the optical isolator 300 includes a Faraday rotator 310, and a polarizer 320 and an analyzer 330, which are polarizing materials, are provided on the front and rear sides of the Faraday rotator 310. The optical isolator 300 further includes a polarizer 320-Faraday rotator 310 -an analyzer 330 arranged in this order on the optical axis 312, and a magnet 340 is mounted on at least one side of the side surfaces of the polarizer 320- And the magnet 340 may be housed in the housing 350. [

Further, the isolator is suitably used for a fiber laser for a processing machine. In other words, it is suitable to prevent the reflected light of the laser beam emitted from the laser element from returning to the element and making the oscillation unstable.

(Example)

Hereinafter, the present invention will be further described with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1 to 63 and Comparative Examples 1 to 15]

According to the method shown in Fig. 1, rare-earth oxide transparent ceramics containing terbium oxide were respectively prepared from the raw materials and conditions shown in Tables 1 to 7 (Examples) and Tables 8 to 9 (Comparative Examples). In Examples 1 to 9, no annealing was performed.

A predetermined amount of a sintering auxiliary agent was added to each raw material powder, and an effective amount of ethyl cellulose and polyvinyl alcohol was added as a dispersant and a binder, and these were mixed by a pot mill to obtain a mixture. Subsequently, the mixture was spray-dried to obtain granules having a particle size of several tens of 탆. After the above granules were used for forming the mold as the primary molding, CIP was performed as the secondary molding to obtain a molded article. The obtained molded body was calcined at 200 to 1,000 占 폚 in the atmosphere, and then calcined (main calcination) at 1,600 to 1,800 占 폚 in a predetermined atmosphere. The obtained fired body was subjected to HIP treatment and, if necessary, annealing treatment to obtain the ceramics (size: 6 mm in diameter, 10 mm in length) of the present invention. The physical properties of the obtained ceramics are shown in the respective tables.

&Quot; Crystal structure after sintering " shown in Tables 1 to 9 indicates whether precipitates observed with an optical microscope were analyzed by EBSD or TEM-XRD to detect only cubic crystals and other phases.

In the transmittance measurement shown in Tables 1 to 9, the sample was optically polished on both sides with a thickness of 10 mm and measured. With respect to the insertion loss, measurement was carried out by optical polishing both surfaces with a sample thickness of 10 mm. Since no anti-reflective coating is performed at this time, reflection loss is included. With respect to the extinction ratio, both surfaces were optically polished with a sample thickness of 10 mm, and measurement was carried out with or without a polarization state.

The sample dimensions after the pressure sintering and annealing were 6 mm in diameter and 12 mm in length and the outer periphery was processed to 2 mm and the both end faces were processed 1 mm each for the outer periphery processing and the end face processing so that the finishing dimensions were 4 mmφ in diameter and 10 mm in length. , Grinding, polishing, etching, and the like.

According to the present invention, it is possible to provide an optical isolator for use in a fiber laser for a processing machine by manufacturing an oxide including terbium oxide defining an average particle diameter, a transmittance of a specific wavelength, an insertion loss, and an extinction ratio.

Fig. 2 shows the &quot; transmittance measurement profile of transparent ceramics &quot; with respect to the relationship between the measurement wavelength and the transmittance including 633 nm and 1,065 nm, which are used wavelengths. The respective curves are plotted in terms of the transmittance of Examples 1 and 11 in relation to the wavelength. All transmittances show a transmittance of 50% or more at wavelengths between 500 and 1,500 nm including 633 nm and 1,065 nm, It can be confirmed that the transmittances at the wavelengths of 600 nm and 1,000 nm specified by the invention reach 55% or more and 70% or more, respectively.

300 optical isolator
310 Faraday rotator
312 optical axis
320 polarizer
330 analyzer
340 magnets
350 housing

Claims (16)

A method for producing a transparent ceramics,
(1) (a) terbium oxide,
(b) at least one oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides,
(c) a sintering aid which does not precipitate the crystal other than the cubic crystal in the crystal structure of the terephthalate-based ceramics
(B) is 40 to 60 mol%, and the oxide of (b) is the remainder of the oxide of (b), in terms of molar ratio of terbium oxide (Tb ₂ O ₃ ) The raw material powder of (a) and (b) and the raw material powder of (c) in which the average primary particle diameter is adjusted in the range of the average primary particle diameter of 30 to 2,000 nm, A first step of obtaining a molded article,
(2) a second step of calcining the shaped body at 400 to 1,000 DEG C in an oxidizing atmosphere to obtain a calcined body,
(3) a third step of obtaining a sintered body by firing the calcined body at 1,400 to 1,700 DEG C in a non-
(4) A fourth method for producing a transparent ceramics characterized by comprising a fourth step of press-firing the sintered body at a temperature of 1400 to 1,800 占 폚 at a temperature of the firing temperature of 19 to 196 MPa to obtain a pressure-sintered body. A method for producing a transparent ceramics,
(1) (a) terbium oxide,
(b) at least one oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxides,
(c) a sintering aid which does not precipitate the crystal other than the cubic crystal in the crystal structure of the terephthalate-based ceramics
(B) is 40 to 60 mol%, and the oxide of (b) is the remainder of the oxide of (b), in terms of molar ratio of terbium oxide (Tb ₂ O ₃ ) The raw material powder of (a) and (b) and the raw material powder of (c) in which the average primary particle diameter is adjusted in the range of the average primary particle diameter of 30 to 2,000 nm, A first step of obtaining a molded body by molding a calcined powder at 400 to 1,000 DEG C in an oxidizing atmosphere,
(2) a second step of obtaining a sintered body by firing the molded body at 1,400 to 1,700 DEG C in a non-
(3) a third step of pressurizing and firing the sintered body at a temperature of 1400 to 1,800 占 폚 at a temperature of the firing temperature or higher and a pressure of 19 to 196 MPa to obtain a pressure-
Wherein the transparent ceramics has a thickness of from about 1 to about 10 nm. 3. The method according to claim 1 or 2,
And the resultant is annealed at 1,500 to 2,000 DEG C under an atmosphere containing no oxygen. 3. The method according to claim 1 or 2,
(c) the sintering aid is an oxide, fluoride or nitride of an element selected from titanium, zirconium, hafnium and calcium. A process for producing transparent ceramics according to any one of claims 1 to 3, which comprises the steps of preparing terbium oxide (Tb ₂ O ₃ ), at least one oxide selected from yttrium oxide, scandium oxide and lanthanide rare earth oxide, Wherein the total amount of terbium oxide and the oxide is 100 mol%, the content of terbium oxide is 40 to 60 mol%, the remainder is the oxide, and the content of the sintering auxiliary is 0.001 To 1% by mass of terephthalate based ceramics,
(1) the crystal structure of the terephthalate-based ceramics does not contain any abnormality other than cubic crystal,
(2) the average crystal grain diameter is in the range of 0.5 to 100 mu m,
(3) The sintering aid as described in any one of (1) to (3) above, wherein the sintering aid contains a sintering aid which does not precipitate a crystal other than cubic one in the crystal structure of the above-
Lt; / RTI &gt; The transparent ceramics according to claim 5, wherein the sintering aid is an oxide, a fluoride or a nitride of an element selected from titanium, zirconium, hafnium and calcium. 6. The method of claim 5,
In the thickness direction of the sample having a thickness of 10 mm,
(1) a linear transmittance at a wavelength of 1,000 nm is 70% or more,
(2) The transparent ceramics characterized in that the linear transmittance at a wavelength of 600 nm is 55% or more. 6. The method of claim 5,
Wherein an insertion loss including a reflection loss of a cross section in a plane of 90% or more of a measurement plane at a wavelength of 1,065 nm is 1.2 dB or less. 6. The method of claim 5,
Wherein an extinction ratio in a plane of 90% or more of the measurement plane at a wavelength of 1,065 nm is 30 dB or more. 6. The method of claim 5,
Wherein the refractive index distribution at the time of measurement of the transmitted wavefront in an area of 90% or more of the measurement surface at a thickness of 10 mm is within 5 10 ^-5 at a wavelength of 633 nm. A magneto-optical device comprising the transparent ceramics according to claim 5. A magneto-optical device in which the transparent ceramics described in claim 5 is used as a Faraday rotation element. A magneto-optical device for use in an optical isolator used in a wavelength region of 1,065 nm with a polarizing material before and after a Faraday rotator in the magneto-optical device according to claim 12. delete delete delete

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